Process for improving folding endurance



United States Patent ()fifice 3,374,715 PROCESS FOR IMPROVING FOLDENGENDURANCE John W. Koning, Jr., Madison, Wis., assignor to the UnitedStates of America as represented by the Secretary of Agriculture NoDrawing. Filed Aug. 18, 1965, Ser. No. 480,826 1 Claim. (Cl. 9336)ABSTRACT OF THE DISCLOSURE This invention relates to a process forimproving the folding endurance of fiberboard containers that have beentreated to increase the strength properties of the container. Theinvention is carried out by prefolding the treated fiberboard prior tocuring the treatment impregnant.

A nonexclusive, irrevocable, royalty free license in the inventionherein described throughout the world for all purposes of the UnitedStates Government, with the power to grant sublicenses for suchpurposes, is hereby granted to the Government of the United States ofAmerica.

A difi'lculty which arises in the use of treated containers, especiallywhere a fiber stiffening agent is used as an impregnant, is theembrittlement of the fiberboard. For example, when corrugated fiberboardcontainers constructed from treated paperboards are set up and the flapsfolded, fracture of the paperboard sometimes occurs at the vertical andhorizontal scorelines, thu resulting in an unfavorable structure.

Accordingly, an object of this invention is to provide a method forpreventing the formation of fractures in a fiberboard container uponbending or folding of said fiberboard.

Other objects which will become apparent to those skilled in the artwill appear in the specification and in the appended claim.

Various agents are used to treat fiberboard for use in structures,depending on the characteristics desired in the final product. Forexample, if corrugated fiberboard is used to construct containers, saidfiberboard may be treated with a variety of agents to increase strengthor to resist the penetration of moisture. Many of the chemical agentsused in treatment become rigid or brittle upon polymerizing orhardening, thereby causing the fiberboard to become embrittled and tocrack or fracture upon bending or folding.

The concept herein described which permits the bend- 3,3 74,715 PatentedMar. 26, 1968 ing or folding of treated areas is that of preworking thetreated fiberboard at the scorelines or other areas where the materialis to be folded, prior to the curing of the impregnant therein. Cineprocedure which may be utilized in the practice of the presentlydescribed invention is as follows:

The fiberboard is treated and cut into any desired shape, depending uponthe structure to be formed therefrom. Prior to the curing of the treatedfiberboard, all areas that are to be folded or bent are preworked bybending said areas to the greatest extent possible. For example, theflaps in a conventional container may be conveniently folded through anarc of at least 330 degrees, while the corners may be folded through anangle of 180 degrees.

After the fiberboard has been thus preworked, the impregnant therein iscured by heat or other suitable means.

In further illustration of this invention, the following example isgiven:

Example Two sets of identical resin treated corrugated fiberboardcontainers were exposed to a temperature of 360 degrees F. for 35minutes in order to cure the impregnant therein. Prior to this exposure,the material was preworked at the scorelines of one set of containers byrotating the panels through an arc of about 180 degrees, and the flapsthrough an arc of about 330 degrees. After exposure to the aforesaidelevated temperature, the containers in each set were set up and theflaps folded in through an arc of about degrees. Severe cracking and, insome instances, complete separation of the fiap from the side panelsoccurred at the scorelines of the set of containers that were notpreworked. The flaps of those containers that had been preworked couldbe folded through an arc of at least 90 degrees without severe cracking.

Having thus described my invention, What is claimed is:

1. The method for improving folding endurance in treated fiberboardcontainers comprising treating the fiberboard containers with astiffening resin, then preworking said containers at the intendedscorelines and folding areas, and then curing said resin.

References Cited UNITED STATES PATENTS 1,897,198 2/1933 Keller 93362,655,082 10/1953 Amyx et al 9352 3,137,436 6/1964 Moors et a1 93363,158,073 11/1964 Rumberger 9336 BERNARD STICKNEY, Primary Examiner.

